Lecture 4.F10

Lecture 4.F10 - Neuroscience 106: Lecture 4 Resting...

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Neuroscience 106: Lecture 4 – Resting Membrane Potential to Action Potential ASSIGNMENT: In Bear et al. study Chapter 4. I. Definitions of terms relating to ion flux and membrane potential: A. Diffusion force is the force on an ion due to its concentration gradient (i.e. the ratio of extracellular to intracellular concentration of an ion). Does not change significantly under physiological conditions . B. Electrostatic force is the force on an ion produced by the membrane voltage. The amount and direction of the force is a function of the membrane voltage and the charge of the ion. C. Driving force on an ion is the sum of the diffusion and electrostatic forces. It is calculated by the formula Vm - E ion (membrane voltage minus ionic E ion ). The driving force is the force that controls the rate of ion flux IF the membrane is permeable to the ion . The ion flux thus alters the Vm. The direction of driving force tells you the direction of current flow: outward is positive, inward is negative. D. Ion flux is the mechanism by which membrane potential is changed. It is controlled by 1) the driving force of an ion, and 2) the permeability of the membrane to that ion. E. Equilibrium potential (E ion ) is a voltage that exactly offsets the diffusional force of the ion. It is the point where diffusion and electrostatic forces counteract each other. It is calculated by the Nernst Equation . IMPORTANT: The membrane potential is always driven toward
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Lecture 4.F10 - Neuroscience 106: Lecture 4 Resting...

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